1. Field of the Invention
One aspect of the invention relates to surgical tools in the form of an elongated shaft and tip suited for use in phacoemulsification surgical instruments and irrigation-aspiration instruments.
2. Discussion of Related Art
Conventional phacoemulsification tips are sharp and have an overly large port that admits the eye capsule in a blink-of-an-eye. The eye capsule, when sucked into the overly large port, puckers and rips to produce rapidly widening tear lines through which vitreous prolapses, which often leads to vitreous loss. Therefore, the use of such conventional phacoemulsification tips that are sharp with the overly large port run the risk of causing capsule ruptures, which is a very serious intraoperaive, i.e., surgical, complication. As an alternative, femto lasers are used (sometimes referred to as femtosecond lasers) to assist cataract surgery procedures.
In an article entitled “Femtosecond Laser Cataract Surgery: Advantages Await Clinical Trial Results” by James Brice and published Nov. 26, 2012, Femtosecond laser cataract surgery are discussed. Excerpts from the article are in the following seven paragraphs.
Femtosecond lasers promise to literally to cut a new edge in terms of the precision and accuracy of incisions made during cataract surgery, according to Calvin Roberts, MD, chief medical officer of Bausch+Lomb. Bausch+Lomb is 1 of 5 companies that produce US Food and Drug Administration-cleared femtosecond laser surgical systems.
Surgery using handheld instruments is the current standard for treating cataracts, which are responsible for nearly 50% of blindness worldwide. The success of this approach depends to a great extent on the surgeon's skill and experience. About 10 million cataract surgeries are performed annually worldwide, according to the World Health Organization. Many of those patients could benefit from a conversion to femtosecond lasers guided by ultra-high-resolution 3-dimensional optical coherence tomography (OCT).
Femtosecond lasers are well suited for cataract surgery because of their ability to tightly focus energy to produce precise surgical incisions, Dr. Roberts said. Cuts of a uniform depth into the lens are possible. The disruptive heat associated with current laser technology is reduced as the laser pulses once every one-trillionth of a second. The ability to focus such energy allows the surgeon to cut deeply on a single plane without collateral damage, he said.
Results of preliminary research are promising. Femtosecond lasers produce continuous anterior incisions for capsulorrhexis that are twice as strong and more than 5 times as precise in size and shape as manual incisions, according a 2010 study by Palanker and colleagues at Stanford University School of Medicine, Stanford, Calif.
Palanker and colleagues' research revealed that segmenting and softening the lens with a femtosecond laser simplifies its emulsification and removal. Three-dimensional cutting of the cornea takes advantage of internal pressure in the eye to create self-sealing incisions, and it allows exact placement of the limbal-relaxing incisions, often performed in the same procedure, that are used to treat astigmatism.
Friedman and colleagues, also at Stanford University School of Medicine, measured the accuracy of an OCT-guided femtosecond laser for cutting specified circles and curved incisions and compared it with manually created capsulorhexis in a small human study. Deviation from the intended diameter of the resected capsule disk was 29 (±26 μm) for the laser technique and 337 μm (±258 μm) for manual incisions. Mean deviations from circularity were 6% for the laser and 20% for manual incisions.
The advantage conferred by this precision can be applied to corneal incisions, anterior capsulotomy, and lens softening and fragmentation before aspiration, noted Roger F. Steinert, MD, chair of ophthalmology at the University of California, Irvine, School of Medicine. “You can't do these things repeatedly or dependably when you are operating manually with a blade,” he said.
Indeed, the safety benefits of femtosecond laser-assisted cataract surgery are mentioned in a further article entitled “Technique yields safety benefits Femtosecond laser-assisted cataract study procedure minimizes corneal trauma” by Cheryl Guttman Krader, reviewed by Zoltan Z Nagy, MD, PhD, and published in Opthalmology Times on Dec. 1, 2012. The article mentions that the increased safety of the femto[second] laser procedure in this study might be attributed to the user of less ultrasound energy during phacoemulsification and was associated with less early corneal edema and better corneal endothelial cell function compared with standard cataract surgery. Average phaco power was reduced by as much as 51% compared to standard cataract surgery and the effective phaco time was reduced by as much as 43% compared to standard cataract surgery.
An intraocular lens, or IOL, is an artificial lens made of plastic, silicone or acrylic that performs the function of the eye's natural lens. Most of today's IOLs are less than a quarter of an inch in diameter and soft enough to be folded so they can be placed into the eye through a very small incision.
There is a need to reduce a risk of causing capsule ruptures, i.e., by avoiding the use of conventional phacoemulsification tips that are sharp and that have an overly large port. That is, there is a need for phacoemulsification tips that are safe in the sense that they are not as likely to cause capsule ruptures. That is, the surgical tool should be “capsule friendly” to lessen the likelihood of creating capsule ruptures during their use in phacoemulsification surgical procedures or in irrigation-aspiration applications of the eye.
There is also a need to score and break-up glossy, coagulated walls, whose glossy, coagulated state resulted from impingement by a laser energy beam during the course of Femtosecond laser-assisted cataract surgery.